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The cluster synchronization of mutually-coupled semiconductor lasers (SLs) network with complex topology is theoretically and numerically investigated, in which stable zero-lag synchronization could be achieved between different SLs within same cluster. It is shown that the symmetry of SLs network topology is an underlying mechanism for the formation of SLs clusters. Different SLs clusters can exhibit different local dynamics and, most importantly, synchronized SLs clusters could coexist with unsynchronized ones. We also discussed the influence of the significant parameters of SLs on the stability of cluster synchronization. The numerical results show that two key internal parameters of SLs, the linewidth-enhancement factor and gain saturation coefficient, play important roles on the SLs network dynamics. It is also shown that, from the point view of symmetry, the self-feedback strength of SLs can play a particularly important role on the formation of SLs cluster. Moreover, the existence of symmetry-induced cluster synchronization is verified in different types of SLs networks topologies (random network and Nepal power grid network), indicating the universality of proposed results. Our results suggest a new insight into the research of synchronized dynamics in complex delay-coupled SLs networks. [ABSTRACT FROM AUTHOR]

Quantum random number is a particularly important physical resource both for quantum communication and quantum cryptography. Quantum randomness amplification, as a key technology in quantum random number generation, has a significant counterintuitive effect: one can amplify weak randomness to almost perfect randomness by quantum systems, which is impossible in classical cryptography. In this letter, we propose an explicit quantum randomness amplification scheme with two untrusted devices, from which we could extract one single perfect random bit from weak random bits. An explicit non-malleable two-source extractor is introduced to extract perfect randomness from two independent min-entropy sources, which are derived from a Bell test with two untrusted devices. The universally composable security of the proposed protocol is proved. [ABSTRACT FROM PUBLISHER]

A key problem of content caching networks is that extra radio resource blocks are consumed to push content objects, which leads to a decline of spectrum efficiency. To solve this problem, a non-orthogonal multiple access-based multicast (NOMA-MC) scheme is proposed in this paper, where pushing and multicasting content objects can be accomplished simultaneously, and thus the spectrum efficiency can be improved significantly. To evaluate the performance of the NOMA-MC scheme, an explicit expression of outage probability is derived, which shows that full diversity gains can be achieved in the single-cell scenario. Moreover, the theoretical results can be extended to the multi-cell scenario by establishing a stochastic geometry-based network model, which show that the NOMA-MC scheme can achieve better performance than the conventional orthogonal multiple access-based multicast scheme. Then, the joint design of power allocation and content matching is studied to enlarge the performance gains of the NOMA-MC scheme, and two distributed optimization algorithms are proposed by solving a hospitals/residents matching problem. Finally, simulation results are provided to verify the analytical results, and also demonstrate the performance gains of the NOMA-MC scheme. [ABSTRACT FROM PUBLISHER]